Despite high rates of drug and other co-occurring mental health problems among American Indian youths, we know little about their service utilization. Their health care system (The Indian Health Service) developed separately from other federal and state programs. Although they are eligible to receive state-funded services, political resistance, difficulty in accessing Medicaid reimbursement, and lack of on-reservation services impede access differentially for urban and reservation-based youths. The AIM- HI (Adolescent American Indian Multisector Help Inquiry) study will collect service use and drug-use information over a 4-year period (from adolescence to young adulthood) on urban and reservation-based American Indian youths. The samples are both from Arizona, providing stability in state financed services, yet one lives on the Salt River Pima-Maricopa Tribal lands and the other in urban Phoenix. The project will interview 1,000 youths in Year 1, sample 400 of the 1,000 for intensive longitudinal interviewing, and survey 600 of these youths' gateway service providers. Multisector service use will be studied in the specialty sectors of drug/alcohol and mental health; the nonspecialty sectors of child welfare, education, juvenile justice, and primary health; the informal sector comprised of parents, relatives and friends; and the traditional sector of Native healers. The study will achieve three aims: 1. To test two service use hypotheses: a) Youths' use of services for their drug or comorbid problems is determined by their need, their predisposing characteristics, and service enabling characteristics; their need as perceived by gateway providers; and those gateway providers' resources, service connections, and service knowledge. and b) After controlling for baseline environmental factors and needs, American Indian youths who have accessed and utilized more extensive and intensive services for their drug use and related behavioral problems will be less likely to have impaired functioning and substance misuse, abuse or dependence. 2. To test a hypothesis concerning the consequences of service reimbursement: The use of specialty substance-use services is positively associated with the availability and accessibility of Medicaid and managed care reimbursement to those services. 3. To document: a) the prevalence, severity and duration of substance abuse and other problems, as well as the protective and risk factors, b) The multisector configurations of services and their complementary or supplementary relationships; and c) The relationship between barriers and changes in the configurations of services. AIM-HI's impact is accelerated by the participation of American Indian community representatives; the association of its PIs with the George Warren Brown School of Social Work's Center for Mental Health Services Research, and the Buder Center for American Indian Studies; and the collaboration of key researchers in the field.